course_zephyr_rtos_rpi_4b

Chapter 2: Introduction to Zephyr - Theory

Introduction | Theory | Lab | Course Home

Now that you understand what Zephyr is and why it’s valuable, let’s dive deep into the technical aspects of the Zephyr ecosystem and development workflow.

The Zephyr Ecosystem

Core Components

Zephyr Kernel: The heart of the system, providing fundamental RTOS services:

Device Driver Framework: Zephyr provides a unified driver model:

Networking Stack: Comprehensive connectivity options:

Build System (West): Modern, Git-based build system:

Development Environment Setup

Recommended IDE: VS Code with Zephyr Extension The Zephyr extension for VS Code provides:

Alternative Development Options:

West Build System Deep Dive

West Workspace Structure:

zephyrproject/                 # West workspace root
├── .west/                     # West configuration and metadata
├── zephyr/                    # Main Zephyr repository
├── modules/                   # External module dependencies
│   ├── hal/                   # Hardware abstraction layers
│   ├── lib/                   # Third-party libraries
│   └── crypto/                # Cryptographic libraries
├── tools/                     # Development tools
└── bootloader/                # MCUboot bootloader

Key West Commands:

# Workspace initialization
west init ~/zephyrproject
west update

# Building applications
west build -b <board> <source-directory>
west build -b rpi_4b zephyr/samples/hello_world

# Flashing and debugging
west flash                     # Flash to connected device
west debug                     # Launch debugger session
west attach                    # Attach to running target

# Configuration and cleaning
west build -t menuconfig       # Open configuration menu
west build -t clean           # Clean build artifacts

Board Selection: Zephyr supports extensive hardware through board definitions:

Configuration System (Kconfig)

Understanding prj.conf: This file configures Zephyr features for your application:

# Enable GPIO driver
CONFIG_GPIO=y

# Enable serial console
CONFIG_SERIAL=y
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

# Enable networking
CONFIG_NETWORKING=y
CONFIG_NET_IPV4=y
CONFIG_NET_TCP=y

# Set application-specific options
CONFIG_MAIN_STACK_SIZE=2048
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=1024

Configuration Categories:

Kconfig Tools:

# Interactive configuration menu
west build -t menuconfig

# Search for configuration options
west build -t guiconfig

# Save current configuration
west build -t savedefconfig

Device Tree Fundamentals

What is Device Tree?

Device Tree is a data structure that describes hardware components and their relationships. In Zephyr, it defines:

Example Device Tree Node:

/ {
    leds {
        compatible = "gpio-leds";
        led0: led_0 {
            gpios = <&gpio0 13 GPIO_ACTIVE_LOW>;
            label = "Green LED";
        };
    };

    buttons {
        compatible = "gpio-keys";
        button0: button_0 {
            gpios = <&gpio0 11 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
            label = "Push button 0";
        };
    };
};

Using Device Tree in Code:

#include <zephyr/devicetree.h>
#include <zephyr/drivers/gpio.h>

#define LED0_NODE DT_ALIAS(led0)
#define BUTTON0_NODE DT_ALIAS(sw0)

static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED0_NODE, gpios);
static const struct gpio_dt_spec button = GPIO_DT_SPEC_GET(BUTTON0_NODE, gpios);

Memory Management

Memory Layout:

Zephyr applications have several memory regions:

Memory Configuration:

# Set main stack size
CONFIG_MAIN_STACK_SIZE=4096

# Enable heap and set size
CONFIG_HEAP_MEM_POOL_SIZE=16384

# Configure system workqueue stack
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

Static vs Dynamic Allocation:

Security Features

Secure Boot Chain:

  1. MCUboot: Secure bootloader with image verification
  2. Image Signing: Cryptographic signatures on application images
  3. Rollback Protection: Prevent downgrade to vulnerable versions
  4. Hardware Security: Trusted Platform Module (TPM) integration

Runtime Security:

Testing and Debugging

Twister Test Framework:

# Run all tests
west twister

# Run tests for specific board
west twister -p rpi_4b

# Run specific test suite
west twister -T tests/kernel/threads

Debugging Tools:

Performance Optimization

Memory Optimization:

Real-time Performance:

This theory section provides the technical foundation needed to understand Zephyr development. Next, we’ll apply this knowledge in a hands-on lab exercise.

Next: Introduction to Zephyr Lab

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